1. Field of the Invention
The present invention relates to a high-frequency module that transmits and receives a plurality of communication signals having different frequency bands using a common antenna, and more specifically to a high-frequency module whose reception signal output terminals for the respective communication signals are constituted by balanced terminals.
2. Description of the Related Art
In the related art, there have been devised various high-frequency modules that transmit and receive a plurality of communication signals having different frequency bands using a common antenna. In such high-frequency modules, for example, as described in Japanese Unexamined Patent Application Publication No. 2009-124746, a common terminal of a switch IC is connected to a common antenna, and a transmission signal input terminal and a reception signal output terminal of a high-frequency module are connected to a plurality of individual terminals of the switch IC.
Some of the high-frequency modules of the related art have a structure in which a SAW duplexer is connected to one individual terminal of the switch IC. In a high-frequency module of this type, reception signals that are two types of communication signals are output from one individual terminal, and are separated by a SAW duplexer so that a reception signal that is each communication signal is output from a different terminal of the high-frequency module.
In a high-frequency module having such a configuration, balanced terminals are often used as reception signal output terminals in accordance with the configuration or the like of a signal processing circuit in a subsequent stage.
In such a case where balanced terminals are used, a wiring pattern is set so that the phase difference between signals output from two terminals constituting the balanced terminals becomes 180°. In the related art, therefore, a wiring pattern as illustrated in FIG. 1A has been used. FIG. 1A is a diagram illustrating a wiring pattern for a SAW duplexer in a high-frequency module of the related art, and FIG. 1B includes graphs illustrating the amplitude characteristics and phase characteristics of a SAW duplexer alone in a high-frequency module having a structure of the related art and of the module.
FIG. 1B illustrates the characteristics of a GSM 900 communication signal, where the phase characteristics are “0” when the phase difference between signals output from two balanced output terminals is 180°.
As illustrated in FIG. 1A, wiring patterns 101P and 102P which form one balanced output from a SAW duplexer S2 have the same line width and the same line length and are formed in parallel. Also, wiring patterns 201P and 102P which form the other balanced output from the SAW duplexer S2 have the same line width and the same line length, and are formed in parallel. In addition, wiring patterns 301P and 302P which form one balanced output from a SAW duplexer S1 have the same line width and the same line length, and are formed in parallel. Also, wiring patterns 401P and 402P which form the other balanced output from the SAW duplexer S1 have the same line width and the same line length, and are formed in parallel.
However, as in the related art, if a pair of wiring patterns which are routing patterns for a balanced output are formed in the same shape in terms of both line length and line width, the pair of wiring patterns are subject to design limitations and therefore design flexibility is reduced. Thus, it is difficult to make the high-frequency module compact. In addition, the design load may be increased.
Additionally, even if the line lengths and the line widths are the same, as illustrated in FIG. 1B, the phase shift may actually deviate from 180°, resulting in occurrence of transmission loss.